The purpose of this study is to investigate the cognitive and physiological basis for cognitive resources such as information processing speed and the selective distribution of attention. Non-demented patients with Parkinson's disease (PD) have cognitive deficits that have been attributed to limitations in cognitive resources, or to modular deficits associated with domain-specific processes. The first Specific Aim investigates these alternatives with on-line measures of single word and sentence processing because language is a familiar domain with high face validity. Group-wide and individual patient analyses are hypothesized to show that PD patients have limitations in information processing speed and directed attention that selectively compromise specific aspects of sentence processing. These findings will contribute to cognitive neuroscience by defining the role of cognitive resources in intellectual functioning from a unique perspective. The second Specific Aim takes advantage of the well-known neurotransmitter and neuroanatomical basis for PD to advance our knowledge of the physiology of cognition. We propose to define the role of dopamine in modular and resource-based aspects of cognition with on-line studies of sentence processing in PD patient who are "on" and "off" the dopamine supplementation. Cerebral recruitment patterns for modular and resource-based processing overlap considerably, and the applicants propose to use functional magnetic resonance imaging (fMRI) to dissociate the anatomic distributions of brain activation for cognitive resources and modular processes during sentence processing challenges in healthy elderly subjects and PD patients. We expect that the dopamine status of PD patients will affect limitations in information processing speed and directed attention that contribute to cognition. The findings will suggest an important pharmacologic strategy for the treatment of a specific cognitive impairment that is common in the elderly. Healthy subjects are expected to recruit partially distinct brain regions for cognitive resources and modular processes during sentence comprehension, including dopaminergic projection zones such as frontal cortex and the striatum of the left hemisphere. PD patients are expected to have limited recruitment of the portion of the normal neural network that supports cognitive resources since PD patients have sentence comprehension difficulty due to their impaired cognitive resources. These findings will contribute to cognitive neuroscience by defining the anatomic basis for cognitive resources and the modular processes that underlie a distributed cerebral network supporting a complex cognitive process.